The invention generally relates to recovering a reactant from a fuel cell exhaust flow.
There are many different types of fuel cells, such as proton exchange membrane (PEM) fuel cells, alkaline fuel cells, molten carbonate fuel cells, direct methanol fuel cells, solid oxide fuel cells and phosphoric acid fuel cells. In its basic function, a fuel cell promotes an electrochemical reaction to produce heat, protons, electrons and water.
Phosphoric acid is a component of a phosphoric acid fuel cell, and as such, the reactants that flow through the phosphoric acid fuel cell contact the phosphoric acid. Thus, exhaust streams from the fuel cell typically carry some trace amounts of phosphorus in the form of phosphoric acid, P2O4, etc.
The exhaust stream from a phosphoric acid fuel cell may contain some concentration of reactants. Therefore, it may be desirable to recover the reactants from the exhaust stream for purposes of improving the fuel cell system's efficiency. A difficulty with this approach, however, is that the exhaust stream contains trace amounts of phosphorus, which may, as examples, poison catalysts of the fuel cell system, as well as contribute to the corrosion of fuel cell system components, such as heat exchangers, plumbing, etc.